X-ray medical imaging is a non-invasive method for inspecting the human body structure and is applicable to rapidly obtaining anatomical information (e.g., the shapes/structures of bones, organs, and soft tissues) of the subject without actually performing dissection or obtaining a histological section for medical diagnoses. The conventional X-ray imaging uses an energy range of higher frequency, which has good recognition capability for bones and soft tissues and is therefore commonly used for skeletal radiography. However, the compositions of soft tissues at different parts of the human body do not differ much from each other. As a result, the difference between the compositions of soft tissues is not obvious in the image of the X-ray energy range of skeletal radiography, and it can hardly be used for medical diagnoses. Thanks to X-ray image digitization that developed in the recent years, it has become possible to radiograph soft tissues. For instance, soft tissues may be inspected by using the phase contrast X-ray imaging (PCXI) technology, which utilizes an X-ray source as the ray source of the phase contrast imaging system.
Generally, the current phase contrast X-ray imaging (PCXI) technology may be roughly categorized into in-line based PCXI and grating based PCXI. Because the grating based PCXI has problems such as high dose, long imaging time, longer imaging distance, it is difficult to meet the standard of clinical use. The micro-focal-spot ray source currently used in the in-line based PCXI is a continuous ray source that generally uses power of 75 W, and the micro focal spot formed is about 50 μm. Compared with the ray source power of 1000 W (the micro focal spot is about 100 μm) or 3000 W (the micro focal spot is about 300 μm) for clinical mammography, the PCXI that uses the current micro-focal-spot ray source does not provide sufficient power for radiographing clinical samples.
In addition, the PCXI mostly uses magnets to focus the electron beam, which further concentrates the heat that accompanies the X-ray generated when the electron beam hits the anode target. In order to avoid meltdown of the anode target, the power of the X-ray source is limited. Thus, how to enhance the power of the X-ray source while reducing the risk of meltdown of the anode target is an important issue in this field.